A polyphenylene ether resin has an excellent mechanical property, electrical property, and thermal resistance, and has an excellent dimensional stability, and therefore it is used in a broad range. However, a processing property of molding thereof by itself is inferior. In order to improve the processing property, the technique of formulating a polyamide therewith is proposed in JP-B-45-997. And even thereafter, various improvements have been added thereto, and at present, it has become a material which has many varied uses.
Having heightened consciousness to environment of recent years as a background, to improve fuel cost of automobiles, study of utilizing a resin as exterior automobile materials has been conducted.
Especially, in Europe, a need has arisen for materials which can be electrostatically coated using the same coating line as that used for a steel plate and thus providing materials with electrical conductivity.
As a conventional prior art concerning exterior automobile materials, it is described, for instance, in JP-A-2-163158, JP-A-4-372656, and JP-A-6-306275, that high balance of a coefficient of linear expansion and an impact resistance is important, and a composition comprising a polyamide resin, a polyphenylene ether, and an inorganic filler is useful.
However, in the above-described conventional prior art, since the coefficient of linear expansion is decreased by adding the inorganic filler, sufficient level of an impact resistance was not attained, and it has not been afforded to a practical use, which has been the actual status.
From the above-described standpoint, the technique wherein improvement in balance of a coefficient of linear expansion and an impact resistance can be attained by using a composition substantially not containing an inorganic filler is required.
JP-A-6-287446 discloses a composition comprising a polyamide, a polyphenylene ether, a styrene type resin and a pigment, wherein yellowing of the composition is reduced by dispersing the pigment in a phase of the polyphenylene ether and the styrene type resin.
However, since the composition obtained by the technique as described in JP-A-6-287446 contains a large amount of a styrene type resin, a coefficient of linear expansion thereof becomes high and an impact resistance thereof is also largely decreased. Also it has not in the least electrical conductivity necessary for electrostatic coating, and therefore it can not be used for exterior automobile parts wherein electrostatic coating is possible.
To provide a polymer alloy of a polyphenylene ether and a polyamide with electrical conductivity, JP-A-2-201811 discloses a technique of making a carbon black present mainly in a phase of the polyamide in a mixture of a polyphenylene ether, a polyamide, and a carbon black.
However, as in the technique as disclosed in JP-A-2-201811, when a large amount of carbon black is formulated in a phase of a polyamide, the polyamide becomes extremely fragile and highly viscous, and therefore an impact resistance and fluidity as a composition are greatly worsened. Also, a coefficient of linear expansion thereof is greatly worsened. This is thought to be because an orientation and a crystallization of the polyamide has been inhibited under the influence of an isotropic filler having electrical conductivity.
Further, in the above-stated conventional prior art, a large amount of swarf which is called as “fines caused by pelletizing” (hereinafter sometimes referred to as “fines”) is generated in a pelletizing step (a step wherein a strand extruded from an extruder is cut to form pellets) on processing. Usually, it is difficult to remove these fines completely.
These fines caused by pelletizing, in a place of fabrication, attach to a pellet drier, a pneumatic transportation lines of a molding machine, a hopper part of a molding machine, etc., which necessitates cleaning upon a change of resin type causing greatly decreased productivity. Therefore, this matter as well as the performance of the above arts has been an item always demanded to be improved.
As above, in the conventional prior art, a material which has excellent electrical conductivity, fluidity, and an excellent balance of a coefficient of linear expansion and an impact resistance, and wherein generation of fines caused by pelletizing is greatly suppressed, has not heretofore been available.
Moreover, exterior automobile materials have many necessary properties in addition to the above-described characteristic properties, and for instance, JP-A-60-65035 describes that high adhesion properties with a coating are also required.
The present invention aims to solve the problems which have not been solved by the above stated prior art.
It is therefore an object of the present invention to provide a resin composition which has excellent electrical conductivity, fluidity, and an excellent balance of a coefficient of linear expansion and an impact resistance, and wherein generation of fines caused by pelletizing is largely suppressed.